Intrauterine Devices

How does an intrauterine device prevent pregnancy?

No one knows exactly how an intrauterine device works. Researchers first suggested that an intrauterine device acted like a foreign body in the uterus, making the uterine lining hostile to the fertilized egg, perhaps through an inflammatory response. Another theory proposed that the presence of the intrauterine device hurried the egg through the fallopian tube, reducing chances for fertilization. If the intrauterine device worked by preventing implantation of a fertilized egg, then researchers would expect to find fertilized eggs in the fallopian tubes of intrauterine device users, but they have instead found inactivated sperm in the uterus.

Nowadays the consensus is that the sperm are inactivated before they even reach the egg. Researchers believe that the progesterone in the Progestasert and Mirena intrauterine devices changes the cervical mucus so that sperm cannot swim upstream to meet the ovum; similarly, it is believed that the copper in the ParaGard makes sperm less vigorous and less able to swim. If intrauterine devices do indeed work by killing or inactivating sperm before they reach the egg, then fertilization never happens. Women who hesitate to use an intrauterine device because they do not want to abort a fertilized egg might reconsider their decision.

What is involved in using an intrauterine device?

Can an intrauterine device fall out or move around in the uterus?

An intrauterine device cannot fall out, but occasionally one moves around or is expelled by the muscular contractions of the uterus, usually during the first few months after insertion. Sometimes this happens during a menstrual period, and occasionally it happens without being noticed. So it is important to inspect the strings regularly, just after your menstrual period perhaps, to be sure that your intrauterine device is still in place.

To check your intrauterine device, reach into your vagina and feel up toward the cervix. The strings are quite thin, about the size of dental floss. They do not hang down like the string of a tampon, but are wedged up against the cervix. If you cannot feel the strings, call your doctor, who can determine the exact location of your intrauterine device with ultrasound imaging or an x-ray. Chances are that the strings have just migrated inside the cervix, but sometimes the intrauterine device has moved. Usually it turns up somewhere inside the uterus, but occasionally one works its way through the wall of the uterus and into the abdominal cavity. This perforation of the uterus is a rare but potentially serious complication, and it can happen without the user’s being aware of it. Surgery may be necessary to remove the intrauterine device. So check the strings frequently.

Does an intrauterine device increase the risk of a tub al pregnancy?

There is no evidence that women who have used an intrauterine device in the past and then become pregnant later have a higher rate of tubal pregnancy than women who used other contraceptives. In fact, some data suggest that women who have used the copper-T before becoming pregnant actually have a lower rate of tubal pregnancy than the general population. However, if you become pregnant with the intrauterine device in place, then you do have a higher-than-average chance of an ectopic (out of the uterus) pregnancy. If you are using an intrauterine device and miss a period, or have a late period with light, scanty bleeding, call your doctor immediately; there is a possibility that you might be pregnant.

Do intrauterine devices interfere with later fertility?

There is no evidence that an intrauterine device impairs fertility unless you have had complications, for example, infection or uterine perforation. Often, though, intrauterine devices are prescribed for women who do not want more children.

How much does an intrauterine device cost?

Intrauterine devices are expensive in the United States. The device itself can cost more than two hundred dollars, plus the expense of an office visit to have it inserted and a follow-up visit six weeks later to check that the strings are in place. Some doctors require two visits at the time of insertion: one to do cultures checking for chlamydia and gonorrhea, and a second visit a week later, when the cultures have been completed, to do a pelvic exam and install the device. The total up-front cost for an intrauterine device can run about three hundred dollars, but there are no ongoing costs. Clinics such as Planned Parenthood usually offer intrauterine devices on a sliding price scale. If the intrauterine device remains in place for a year, the cost is similar to that of birth control pills. If it remains in place longer, it becomes less expensive per year than birth control pills. Abroad, an intrauterine device costs only about forty dollars.

The manufacturers of the leading intrauterine devices in this country claim that the high cost results from passing on to the consumer the expense of carrying malpractice insurance against possible lawsuits. Given the many past lawsuits, the assumption of future lawsuits is realistic. The company that makes ParaGard asks women to sign a consent form stating that they are familiar with the product’s possible side effects and risks.

What are advantages and disadvantages of an intrauterine device?

Although the Progestasert and Mirena actually seem to decrease flow during menstrual periods, other intrauterine devices including the ParaGard can cause long and heavy menstrual periods. These symptoms are usually most noticeable during the first year of intrauterine device use and often decrease with time. The initial cost of an intrauterine device is high and the insertion process can be uncomfortable. Some researchers believe that women who use an intrauterine device, especially those who have more than one sexual partner, have a higher rate of pelvic inflammatory disease than those who choose other contraception. The rate is highest just after insertion and up to four months afterward. If you use an intrauterine device and have any of the symptoms of pelvic inflammatory disease (abdominal pain, pain during intercourse, a foul-smelling vaginal discharge, nausea, or vomiting), call your doctor immediately. An intrauterine device will not protect against sexually transmitted diseases.

The advantages are that, once in place, an intrauterine device continues its work without your thinking about contraception at all. intrauterine devices are reliable and effective. They are long-lasting: eight to ten years with the ParaGard, one year with Progestasert, five with Mirena.

Is an intrauterine device the right contraceptive for you’?

Maureen is 37 years old. She has two children and doesn’t want any more, but emotionally she is unwilling to consider sterilization. She is also unable to stop smoking. She and her husband have an active sex life and neither wants to bother with barrier methods.

An intrauterine device would be perfect for Maureen. She and her husband are monogamous, so she doesn’t need protection from sexually transmitted diseases. Because she smokes and is older than 35, she cannot use oral contraceptives.

Although sometimes intrauterine devices are prescribed for a woman who may want children later, they are most often given to women who have completed their families. Mutual monogamy is a must for intrauterine device users, since the intrauterine device gives absolutely no protection against human immunodeficiency virus or any sexually transmitted disease. Women with multiple sexual partners and women whose partners have multiple partners should use barrier methods of contraception.

You should not use an intrauterine device if you have had pelvic inflammatory disease or an ectopic pregnancy. If you have vaginal bleeding of unknown cause or a vaginal infection, you should wait until these conditions have been investigated and cured before getting an intrauterine device. Choose another form of contraception if you have a condition like leukemia or human immunodeficiency virus that makes you susceptible to infection, or rheumatic heart disease that makes your heart vulnerable to infection. You should not use an intrauterine device containing copper if you are allergic to copper.

If you have a strong vasovagal reflex, you probably should not choose an intrauterine device, because of problems with insertion and removal. Once the intrauterine device is in place, however, you probably will not have difficulties. If you have never had a child, your doctor may find it difficult or be unable to insert an intrauterine device.


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